Passing Loop Clearance

[DavidLong]

Fairly simple question. Single track main running line with a passing loop that gives access to an exchange siding. What is the minimum track centre (or equivalent '6 foot' way) required between loop and running line? Note that the loop will not be used for passing two passenger trains but may have a freight train on it when a passenger service passes on the main.

By the way, I've never been sure if the '6 foot' is measured from the inside or the outside of the two running rails.

 

Thanks in advance.

 

David

[The Stationmaster]

Assuming the loop is a running line (which is what you imply) it is 6 feet, measured between the outside edges of the rail (and not measured from the running faces of the rail).

[Grovenor]

And bear in mind that the 6ft is only 6ft if the track is UK standard gauge*. So use of narrow gauges requires this dimension to be increased.

It is easier to apply if the centre to centre spacing is calculated (4'8.5" + 6' + (2 x 2.75") = 11' 2".

Regards

 

*Ignoring Brunel Gauge, modellers of that will know the relevant figures.

[DavidLong]

Grovenor, on 14 Dec 2015 - 12:56, said:

And bear in mind that the 6ft is only 6ft if the track is UK standard gauge*. So use of narrow gauges requires this dimension to be increased.

It is easier to apply if the centre to centre spacing is calculated (4'8.5" + 6' + (2 x 2.75") = 11' 2".

Regards

 

*Ignoring Brunel Gauge, modellers of that will know the relevant figures.

 

Thanks. This would fit with the standard double track spacing for 2FS on Templot of 22.33mm. As some of my stock is 1:148 I would normally use 23mm (in lieu of 22.997!)

 

David

[DavidLong]

Assuming the loop is a running line (which is what you imply) it is 6 feet, measured between the outside edges of the rail (and not measured from the running faces of the rail).

 

Thanks, Mike. This is basically the standard track centres for double track but in some circumstances it was not allowed for such a loop to be used for passing two passenger trains. The example that comes to mind is at Bluntisham on the Ely to St Ives railway. Here is a quote from the Peter Paye book:

"Alongside the loop the railway erected a goods shed. Because of the restricted clearance of this shed it was only permissible to pass a goods and a passenger train at Bluntisham and not two passenger trains. This unofficial instruction also required the goods train to be shunted in the loop siding to allow the passenger train to pass on the single line".

I've never been very clear as to the real nature of the problem here. At first it seems to be clearance with the goods shed but then goes on to say that the goods train had to be in the loop siding (which was just an extension of the loop).

In my case wagons may be left standing on the loop while some are detached to be placed in the exchange siding which is parallel to the loop. The exchange siding and loop I have placed at 15' centres.

 

David

[The Stationmaster]

Thanks, Mike. This is basically the standard track centres for double track but in some circumstances it was not allowed for such a loop to be used for passing two passenger trains. The example that comes to mind is at Bluntisham on the Ely to St Ives railway. Here is a quote from the Peter Paye book:

"Alongside the loop the railway erected a goods shed. Because of the restricted clearance of this shed it was only permissible to pass a goods and a passenger train at Bluntisham and not two passenger trains. This unofficial instruction also required the goods train to be shunted in the loop siding to allow the passenger train to pass on the single line".

I've never been very clear as to the real nature of the problem here. At first it seems to be clearance with the goods shed but then goes on to say that the goods train had to be in the loop siding (which was just an extension of the loop).

In my case wagons may be left standing on the loop while some are detached to be placed in the exchange siding which is parallel to the loop. The exchange siding and loop I have placed at 15' centres.

 

David

David it sounds to me as if the loop was not signalled to passenger standards hence passenger trains were not allowed to use it - in reality a not unusual situation and in some ways one which reflects the greater density of freight traffic on the railway of the distant past.

[Peter Kazmierczak]

Regarding the 6ft distance.

 

As mentioned above, since many of us use 16.5mm gauge (if modelling in 4mm), it seems to me that often this distance just looks wrong on a model. It often makes the tracks look too far apart - unless you're modelling ex-GW broad gauge lines where distances might be greater.

 

I think a more visual approach is sometimes required, rather than religiously following a specific prototype dimension.

[martin_wynne]

Fairly simple question. Single track main running line with a passing loop that gives access to an exchange siding. What is the minimum track centre (or equivalent '6 foot' way) required between loop and running line? Note that the loop will not be used for passing two passenger trains but may have a freight train on it when a passenger service passes on the main.

 

Hi David,

 

The normal spacing for a goods loop off single-track is 10ft way (or 9ft way if space constraints make it unavoidable). By a goods loop here is meant a track or siding alongside a running line where trains come to a stand and staff may be on the ground.

 

For a double-track running line at 6ft way, the side loop spacing should be 10ft way even if it is a normal running line. You can't have two 6ft-way spacings in succession, in multiple track the tracks alternate in pairs at 6ft, 10ft way. Here is a good picture of that, on the cover of this book:

 

 

6ft way means tracks are at 11ft-2in centres.

9ft way means tracks are at 14ft-2in centres.

10ft way means tracks are at 15ft-2in centres.

 

(On GWR and BR(W) lines add 1/2" to those centres -- 6ft way on the GWR means 6ft-6in to the gauge face of the rails, which are 2.3/4" wide.)

 

I shall now leave a space for everyone to post pictures of exceptions.

 

 

 

 

regards,

 

Martin.

[DavidLong]

martin_wynne, on 14 Dec 2015 - 18:38, said:

Hi David,

 

The normal spacing for a goods loop off single-track is 10ft way (or 9ft way if space constraints make it unavoidable). By a goods loop here is meant a track or siding alongside a running line where trains come to a stand and staff may be on the ground.

 

 

Martin.

 

Thanks, Martin. I had a suspicion that my goods loop wasn't far enough away from the running line hence my question. Bit of adjustment required on the Templot plan!

 

David

[The Johnster]

The 6 foot is actually the minimum distance by which running lines are separated, measured from the 'outside' railhead to the adjoining one, and is one of the very sensible ideas we have inherited from George Stephenson's Liverpool and Manchester Railway.  While it is referred to as the '6 foot' it is almost always more than that and 10 feet is more common on fast main lines.  Similarly, the '4 foot' is the distance between the rails in usual railway parlance, though it is of course 4'8 and a half inches.  

 

It is at this point that somebody is going to point out that the distance between the rails is a scale 4 feet if you are working in 00 gauge, unless you want to argue about .5mm, and a debate will start as to the merits of 00, British H0, EM, P4, Scalefour, and so on, but I do not want to start it.

 

Oh dear, looks like I just have...

[Chris116]

It is also worth remembering that in many places the 6 foot is in fact less than that even in places where passenger trains pass each other. The loop through the platforms at Ropley on the Mid Hants Railway is just one of the many examples I know about.

[Grovenor]

 

While it is referred to as the '6 foot' it is almost always more than that and 10 feet is more common on fast main lines.

Could you support that statement? My experience of UK practice is that 6ft is very much the most common spacing for double tracks, and for the pairs where there are multiple tracks.

Clearly HS1 is an exception as it has to take European size trains, but even then I don't think its as much as 10ft.

Regards

[The Stationmaster]

Could you support that statement? My experience of UK practice is that 6ft is very much the most common spacing for double tracks, and for the pairs where there are multiple tracks.

Clearly HS1 is an exception as it has to take European size trains, but even then I don't think its as much as 10ft.

Regards

 

The only places I know where the '6 foot' is significantly more than 6 feet is on former GWR lines at station platforms where there was a 6 foot interval between broad gauge lines and if platforms were not altered the interval between the running lines obviously increased when the gauge was narrowed.  It is one way of easily distinguishing which side of some quadruple track Western stations was originally the broad gauge side as quadrupling in some cases was only to the narrow (by GW standards) gauge.

 

However generally, until layout alterations in the past couple of decades some Western 'ten foot' measurements were probably greater and of course the geometry of curves dating from quadrupling also affected that.

[APOLLO]

Previous thread here

 

http://www.rmweb.co.uk/community/index.php?/topic/50616-the-6ft/&do=findComment&comment=584814

 

Brit15

[Edwin_m]

The 6 foot is actually the minimum distance by which running lines are separated, measured from the 'outside' railhead to the adjoining one, and is one of the very sensible ideas we have inherited from George Stephenson's Liverpool and Manchester Railway.  While it is referred to as the '6 foot' it is almost always more than that and 10 feet is more common on fast main lines.  Similarly, the '4 foot' is the distance between the rails in usual railway parlance, though it is of course 4'8 and a half inches.  

 

It is at this point that somebody is going to point out that the distance between the rails is a scale 4 feet if you are working in 00 gauge, unless you want to argue about .5mm, and a debate will start as to the merits of 00, British H0, EM, P4, Scalefour, and so on, but I do not want to start it.

 

Oh dear, looks like I just have...

 

I believe the "six-foot" on the Liverpool and Manchester was originally 4'8.5", because there was an idea of running out-of-gauge loads on the middle pair of rails where clearances to structures would be greater.  I don't know if this ever happened and it strikes me as impractical and highly dangerous in an era when there was no signalling to speak of.  Not to mention requiring some "interesting" switch and crossing work! 

 

I agree most lines outside GWR territory have the six-foot close to the minimum.  Staff safety wasn't such a consideration in the days when trains were slower and working-class lives were cheaper, and widening the formation by a couple of feet would have a significant impact on the shareholders' pockets.  There are a few lines (such as most of Bolton to Lostock) where the two remaining tracks have been spaced across a former four-track formation and the six-foot is significantly wider.  This may be related to providing access for maintenance during single line working, and also maximising clearances at the twin-arch bridges for any future electrification (now happening but I believe the track is being lowered anyway!). 

[kevinlms]

Hi David,

 

The normal spacing for a goods loop off single-track is 10ft way (or 9ft way if space constraints make it unavoidable). By a goods loop here is meant a track or siding alongside a running line where trains come to a stand and staff may be on the ground.

 

For a double-track running line at 6ft way, the side loop spacing should be 10ft way even if it is a normal running line. You can't have two 6ft-way spacings in succession, in multiple track the tracks alternate in pairs at 6ft, 10ft way. Here is a good picture of that, on the cover of this book:

 

 

6ft way means tracks are at 11ft-2in centres.

9ft way means tracks are at 14ft-2in centres.

10ft way means tracks are at 15ft-2in centres.

 

(On GWR and BR(W) lines add 1/2" to those centres -- 6ft way on the GWR means 6ft-6in to the gauge face of the rails, which are 2.3/4" wide.)

 

I shall now leave a space for everyone to post pictures of exceptions.

 

 

 

 

regards,

 

Martin.

Here's one!

 

https://en.wikipedia.org/wiki/West_Coast_Main_Line#/media/File:Pendolino_and_Freight_train.jpg

 

The LNWR was the first to multiply their original double track main lines. They just used the standard spacing for additional mainlines & so the 3rd & 4th lines had the minimum '6ft' spacing.

 

It was a major mistake & over the years proved to be a nuisance, as it meant track works, often meant that the adjacent mainline had to be closed too.

 

So every one else benefited from the LNWR's pioneering error.

[kevinlms]

Fairly simple question. Single track main running line with a passing loop that gives access to an exchange siding. What is the minimum track centre (or equivalent '6 foot' way) required between loop and running line? Note that the loop will not be used for passing two passenger trains but may have a freight train on it when a passenger service passes on the main.

By the way, I've never been sure if the '6 foot' is measured from the inside or the outside of the two running rails.

 

Thanks in advance.

 

David

Some useful dimensions can be found here, but other scales will need to modify the scale equivalents. The generic prototype distances are given, so not hard to work out.

 

http://www.gauge0guild.com/manual/07_D7_1_1.pdf

[Dungrange]

Some useful dimensions can be found here, but other scales will need to modify the scale equivalents. The generic prototype distances are given, so not hard to work out.

 

http://www.gauge0guild.com/manual/07_D7_1_1.pdf

 

What is a 'catch siding'?  I notice that this document refers to 10' between and mainline and siding, but only 6' between a mainline and a catch siding.

[Northroader]

One consideration which hasn't been mentioned is that all the talk has been prototype practice. If your model loop is placed on anything of a curve, you'll need to increase the spacing.

[beast66606]

Thanks, Mike. This is basically the standard track centres for double track but in some circumstances it was not allowed for such a loop to be used for passing two passenger trains. The example that comes to mind is at Bluntisham on the Ely to St Ives railway. Here is a quote from the Peter Paye book:

"Alongside the loop the railway erected a goods shed. Because of the restricted clearance of this shed it was only permissible to pass a goods and a passenger train at Bluntisham and not two passenger trains. This unofficial instruction also required the goods train to be shunted in the loop siding to allow the passenger train to pass on the single line".

I've never been very clear as to the real nature of the problem here. At first it seems to be clearance with the goods shed but then goes on to say that the goods train had to be in the loop siding (which was just an extension of the loop).

In my case wagons may be left standing on the loop while some are detached to be placed in the exchange siding which is parallel to the loop. The exchange siding and loop I have placed at 15' centres.

 

David

 

Bluntisham was a single platform, with a single line passing it - the loop was for the goods shed which had a canopy over the loop which would account for the limited clearance and hence was not suitable for passing passenger trains, the instructions were probably provided in case problems caused the bobby to be tempted to put a passenger into the loop. I suspect the "loop siding" and loop were one in the same.

[Izzy]

I have always been under the impression that most dimensions for both the standard structure gauge and platform structure gauge, (all minimum recommended figures), were based upon track centre distance rather than from the rail. This was certainly how I drew them up many years ago when they were published in a magazine. Some platform ones gauge from rail or sleeper edge, but are mainly a sub-set of the standard structure gauge.

 

With respect to track centres my understanding, which may well be incorrect, is that the 4'/6'/10' way references were general day-to-day working ones as the other figures, gauge etc, weren't generally as varied as model ones, but of course altered as needed being just minimal ones for straight track and increasing with track curvature and inclination, as would structure clearance.

 

Quadrupled track was usually laid as pairs of running lines with extra distance between - 15'2"/10' way - to provide space for signal post erection and save gantry use. This distance was also often used between any two lines where trains may stop and be inspected/shunted on a normal/regular basis. But of course all was subject to local needs and conditions and could thus vary quite a bit.

 

Izzy

[The Stationmaster]

I have always been under the impression that most dimensions for both the standard structure gauge and platform structure gauge, (all minimum recommended figures), were based upon track centre distance rather than from the rail. This was certainly how I drew them up many years ago when they were published in a magazine. Some platform ones gauge from rail or sleeper edge, but are mainly a sub-set of the standard structure gauge.

 

With respect to track centres my understanding, which may well be incorrect, is that the 4'/6'/10' way references were general day-to-day working ones as the other figures, gauge etc, weren't generally as varied as model ones, but of course altered as needed being just minimal ones for straight track and increasing with track curvature and inclination, as would structure clearance.

 

Quadrupled track was usually laid as pairs of running lines with extra distance between - 15'2"/10' way - to provide space for signal post erection and save gantry use. This distance was also often used between any two lines where trains may stop and be inspected/shunted on a normal/regular basis. But of course all was subject to local needs and conditions and could thus vary quite a bit.

 

Izzy

 

The root of all dimensions is really the prototype although it has obviously be varied, for whatever reason, by those drawing up details for modellers so it has always seemed natural to me - as a railwayman- to follow the practice of the real world in referring to dimensions such as the 'six foot'.  So going back to the 1902 issue of the Requirements  it is very clear  that  'The intervals between adjacent lines of rails where there are two lines only, or between lines of rails and sidings not to be less than 6 feet.  Where additional running lines of rails are alongside the main lines, an interval of not less than 9 feet 6 inches to be provided, if possible, between those additional lines and the main lines'   (these were in fact the 1892 Requirements amended).   Going back even further the GWR construction plans for broad gauge double line showed a distance of 6ft 2.5inches between the running faces.

 

It is not clear if these issues included diagrams in respect of dimensions but I suspect they did appear with the 1920s issue and were certainly included in the 1950 issue.  And in the 1950 issue they do include centre-to-centre measurement for double line but the 10 foot dimension, successor to the 9ft 6" mentioned above, is not quoted as a centre-to-centre figure but simply as, literally, 10 feet (which may be reduced to 9 feet 'in cases of special difficulty'); I can find no mention of 15'2" centres.  But the text of the 1950 issue makes no mention of centre-to-centre distances and refers only to the measurements of the intervals.   And let's face it surely it is that distance, the interval, which is the one that can be most accurately measured on the ground rather than fiddling around establishing centre on all lines and is of course in clearance terms the most important.

 

Thus I can't really understand the model world's fascination with measuring track centres except perhaps when doing any initial setting out for a layout. 

[martin_wynne]

Thus I can't really understand the model world's fascination with measuring track centres except perhaps when doing any initial setting out for a layout. 

 

Hi Mike,

 

It's because we have different gauges in use -- 0, 00, EM, etc., which are not scale equivalents of prototype track gauge.

 

But the width of our rolling stock is generally a scale equivalent, and needs the scale equivalent clearance between passing trains.

 

The interval between the rails in double track therefore has to be amended to create the prototype minimum track centres at our gauge in use.

 

The figures are:

 

double track centres minimum -- 11ft-2in -- 44.67mm centres in 00, EM, P4.

loops and sidings alongside running lines, and pairs of double tracks -- 15ft-2in -- 60.67mm centres in 00, EM, P4.

 

On the GWR and BR(W) add 1/2" to 11ft-2.1/2in -- 44.83mm centres in 00, EM, P4. This is a legacy from the use of 3" wide rails, with 6ft way between them.

 

Martin.

[Izzy]

Thus I can't really understand the model world's fascination with measuring track centres except perhaps when doing any initial setting out for a layout. 

 

Hi Mike,

 

As Martin says it's useful when the model track gauge is less than the prototype. These measurements are also quite handy for double-checking as track is laid (especially when you make it yourself), for they can be used to ensure correct rail to rail distance, and works irrespective of the particular gauge whatever scale you are using, whereas of course the 'ways' fall down with under-gauged track for all clearances, structure/platform etc.

 

Izzy

[Trog]

 

 

The LNWR was the first to multiply their original double track main lines. They just used the standard spacing for additional mainlines & so the 3rd & 4th lines had the minimum '6ft' spacing.

 

It was a major mistake & over the years proved to be a nuisance, as it meant track works, often meant that the adjacent mainline had to be closed too.

 

So every one else benefited from the LNWR's pioneering error.

 

I don't think the existence of the middle six foot space which was usually referred to as the ten foot even though it was only six feet wide was a problem on the WCML until modern safety rules came in. Up until then we just worked up to the sleeper ends of the open road protected by a 20MPH speed restriction and the old rule T4.  A bigger problem was perhaps that the widening was done on the cheap, with the amount of extra land required being reduced by steepening the bank sides, this made slips more likely.